IN VIVO STUDIES CORE DEFINITION The objective of the In Vivo Studies Core is to provide a venue for focusing the human resources, facilities, new technology and equipment necessary for in vivo study of humans and animals. The Core serves to fully integrate investigations at the molecular, cellular and organ system level that are currently performed within the other Cores of the Center. The Core is organized to bring together expertise and in vivo techniques from different disciplines to investigate the role of peptide hormones in a wide variety of gastrointestinal functions. Toward these goals, the major services provided by the In Vivo Studies Core are as follows: 1. To make available a wide variety of acute and chronic animal models for in vivo evaluation of the biological actions of peptide hormones. 2. To examine the physiological changes in mouse models following transgene expression or gene mutation. 3. To provide various in vivo techniques and tests for the investigation of the physiology and pathophysiology of gastrointestinal peptides in man. 4. To facilitate innovations in methodology and to develop new and sophisticated techniques for in vivo studies. 5. To provide education and consultation on the application of in vivo techniques so that basic physiological and biochemical questions pertaining to peptide hormones may be answered.